The disclosed method is an innovative new seamless instant registration method by which a roaming UE that is in Automatic Network Selection mode and registered on a non-preferred visited network, can be forced to immediately register seamlessly within seconds onto another available more preferred visited network. The general method by which this can be accomplished is by updating a specific file in the UICC with specific content, followed by a sending a specific REFRESH command to the ME. This method can be deployed using either a commercial OTA solution or a SIM Toolkit Application in the UICC.
When a roaming UE is powered on in a foreign country with multiple visited networks available, for which registration is possible (due to bilateral network agreements), if the ME is set to Automatic Network Selection mode (which typically is the default setting), the ME follows the Network Selection Procedures outlined in 3 GPP TS 23.122 clause 4.4.3.1 and 4.4.3.3.
There are some scenarios where if the OPLMNwAcT preferred roaming list in the UICC is empty or not updated with the latest more preferred network, then the roaming UE may register onto a less preferred visited network that the home operator would not want their client's UE to register onto. Reasons may be higher roaming costs and/or fewer services such as 3 G data offered on the less preferred network.
In these scenarios, the following United States patent documents generally describe an OTA network based solution in which to steer a clients UE (i.e. via OTA updates to the LOCI and PLMN list followed by a REFRESH) to a more preferred visited network: U.S. Pat. No. 7,127,245 Almgren and U.S. Pat. No. 7,139,570 Elkarat et al.
However, the specific method for how to accomplish the seamless and instant registration behaviour of the UE onto the more preferred visited network after the OTA update is not covered in these patents, for which the descriptions and claims presented in these Prior Arts are obscure and ambiguous in this regard and leave the reader who is skilled in this subject matter area to spend countless hours experimenting and testing with different REFRESH command combinations with different combinations of LOCI updates.
Described are some examples of the challenges and limitations of the at least some previous methods. First, if the LOCI file is updated with the PLMN ID of the preferred visited network, but the Location update status byte 11 is set to a value other than “00”, then seamless and instant registration will not work for all MEs, regardless of which REFRESH command is used after the LOCI file is updated. Second, if the LOCI file is updated with the PLMN ID of the preferred visited network, but the TMSI value of “FF FF FF FF” is specified in bytes 1 to 4, then seamless and instant registration will not work in some MEs, even if used with REFRESH—3G Session Reset. Third, even if the LOCI file is properly updated by updating the PLMN ID of the preferred PLMN, while keeping the TMSI and Location update status intact with the previous values (i.e. non-“FF FF FF FF” TMSI value and Location update status set to “00”), usage of REFRESH—File Change Notification will not accomplish instant registration onto the preferred network on all MEs. Fourth, even if the LOCI file is properly updated by updating the PLMN ID of the preferred PLMN, while keeping the TMSI and Location update status intact with the previous values, usage of REFRESH—UICC Reset will not accomplish seamless and instant registration on MEs that implement a “Cold Reset” procedure, in which the ME performs a powercycle which will give the client the perception that the UE has malfunctioned. Fifth, only REFRESH—3G Session Reset specifies a re-initialization of a network connection through the MM Restart Procedure as per 3GPP TS 31.111 clause 6.4.7. As such, it is not guaranteed and required as per 3 GPP standards (unless there is an IMSI change as per 3 GPP TS 11.14 clause 6.4.7.1) that all MEs using other REFRESH commands, will perform a new network selection attempt on the preferred PLMN using the updated LOCI, even if the LOCI file is properly updated by updating the PLMN ID of the preferred PLMN, while keeping the TMSI and Location update status intact with the previous values.
Therefore, the disclosed method is a novel improvement to these methods, which focuses on only updating the MCCMNC content in the LOCI file with the preferred PLMN while keeping the TMSI and Location update status intact with the previous values, followed by a REFRESH—3 G Session Reset command to the ME, in order to obtain immediate registration within seconds, for which there is no precedence.
Furthermore, the method for seamless instant registration through an MCCMNC update to the LOCI file followed by REFRESH—3G Session Reset to the ME, can also be accomplished through a SIM Toolkit application, in which perhaps the user, via a SIM Toolkit menu in the ME UI, selects the current visited country from a list of countries shown followed by selecting a predefined Network Name associated to the preferred PLMN code of the selected visited country. Once selected, the SIM Toolkit app proceeds with carrying out the disclosed method.
In conjunction to using the method for seamless instant registration onto the preferred visited network, the OPLMNwAcT file in the UICC can also be updated (i.e. using either OTA solution or SIM Toolkit) with the preferred visited network PLMN ID as higher priority over other PLMN IDs (if populated in the OPLMNwAcT list) of the same visited country, followed by sending the REFRESH—3 G Session Reset command to the ME. This will help keep the UE registered on the preferred visited network, if available, during an HPPLMN rescan.
In the future, a new REFRESH command requirement specified in 3 GPP Release 7, REFRESH—Steering of Roaming, is aimed to provide similar instant and seamless registration behaviour as the disclosed method. However, REFRESH—Steering of Roaming is only applicable to Release 7 and higher MEs, and is not specified to work with today's current MEs, most of which are pre-Release 7. Therefore, the practicality of this new REFRESH command is not yet feasible.